Combines having rotating concave threshing systems are known in the art. These types of combines utilize a rotating rotor assembly positioned within a rotating concave assembly. Since combines encounter wide ranges of harvesting situations and crops, it is important to provide a harvesting mechanism that collects the crop in the minimum amount of time with the least losses and product damage. It has been determined that feed rate into the threshing mechanism is a very important factor affecting grain losses and/or damage. Grain losses increase as the feed rate increases. Many times these losses are due to overloading of materials entering the threshing mechanism which results in stalls and/or clogging. The rotating concave threshing system has proved helpful in overcoming these problems to some extent.
Some known threshing systems have used multi-ratio gear type transmissions to drive the rotor assembly with several distinct ratios between the engine speed and rotor assembly speed. Other threshing systems have used bulky, complex, infinitely variable drive systems. It is desirable to have an inexpensive infinitely variable drive speed for the rotor assembly relative to the engine while maintaining constant engine speed for other machine functions.
The present invention is directed to overcome one or more of the problems as set forth above.